This invention relates to certain water soluble halogen-containing compounds and the preparation of said compounds. These compounds are particularly useful as antifoggants in silver halide photographic materials. These compounds are also useful as water-soluble reagents useful for the bromination of organic chemicals. It is also anticipated that these compounds may be useful as water-soluble oxidants and water-soluble antimicrobial agents.
Problems with fogging have plagued the photographic industry from its inception. Fog is a deposit of silver or dye that is not directly related to the image-forming exposure, i.e., when a developer acts upon an emulsion layer, some reduced silver is formed in areas that have not been exposed to light. Fog can be defined as a developed density that is not associated with the action of the image-forming exposure, and is usually expressed as xe2x80x9cD-minxe2x80x9d, the density obtained in the unexposed portions of the emulsion. Density, as normally measured, includes both that produced by fog and that produced as a function of exposure to light. It is known in the art that the appearance of photographic fog related to intentional or unintentional reduction of silver ion (reduction sensitization) can occur during many stages of preparation of the photographic element including silver halide emulsion preparation, spectral/chemical sensitization of the silver halide emulsion, melting and holding of the liquid silver halide emulsion melts, subsequent coating of silver halide emulsions, and prolonged natural and artificial aging of coated silver halide emulsions. The chemicals used for preventing fog growth as a result of aging or storage are generally known as emulsion stabilizers.
The control of fog, whether occurring during the formation of the light-sensitive silver halide emulsion, during the spectral/chemical sensitization of those emulsions, during the preparation of silver halide compositions prior to coating on an appropriate support, or during the aging of such coated silver halide compositions, has been attempted by a variety of means. Mercury-containing compounds, such as those described in U.S. Pat. Nos. 2,728,663; 2,728,664; and 2,728,665, have been used as additives to control fog. Thiosulfonates and thiosulfonate esters, such as those described in U.S. Pat. Nos. 2,440,206; 2,934,198; 3,047,393; and 4,960,689, have also been employed. Organic dichalcogenides, for example, the disulfide compounds described in U.S. Pat. Nos. 1,962,133; 2,465,149; 2,756,145; 2,935,404; 3,184,313; 3,318,701; 3,409,437; 3,447,925; 4,243,748; 4,463,082; and 4,788,132 have been used not only to prevent formation of fog, but also as desensitizers and as agents in processing baths and as additives in diffusion transfer systems.
However, despite all the efforts in this field there still remains a need for compounds which act as effective antifoggants in photographic elements which are stored under high temperature conditions. There is particularly a need for antifoggants which are water soluble and thus are safer to utilize during manufacture of the photographic elements.
In addition, a problem which has faced synthetic organic chemist is the availability of a reagent for brominating organic chemicals that can be handled safely and is stable when dissolved in water, i.e. a brominating reagent that does not react with water when it is dissolved in water. Molecular bromine is a useful brominating agent but it is not very soluble in water and the toxic liquid is often difficult to handle. Other brominating agents such as the commercially available 1,3-dibromo-5,5-dimethylhydantoin are sometimes sensitive to moisture.
This invention provides compounds represented by the following Structure I:
xe2x80x83R1xe2x80x94SO2xe2x80x94C(R2)R3xe2x80x94(CO)mxe2x80x94(L)nxe2x80x94SGxe2x80x83xe2x80x83I
wherein R1 is an aliphatic or cyclic group, R2 and R3 are independently hydrogen or bromine as long as at least one of them is bromine, L is a divalent linking group, m and n are independently 0 or 1, SG is a solubilizing group with a pKa of 8 or less, with the proviso that when m and n are both 0, SG is not a sulfo (or salt thereof) or a sulfonamido (or salt thereof and when m and n are both 1, either L is not an alkylene group or SG is not a carboxy (or salt thereof).
The compounds of this invention reduce fogging during chemical sensitization of silver halide photographic elements. They further enhance fog retardation of liquid emulsions during high temperature holding. The water soluble antifoggants minimize the need for expensive and time-consuming preparation of solid-particle dispersions, as well as minimize the need for volatile organic solvents. Use of these materials also eliminates the need to use environmentally undesirable heavy metal antifoggant salts such as mercuric salts. It is also believed that these compounds may have utility as antifoggants and stabilizers for thermographic and phototbermographic elements. They may also be useful as brominating agents in the preparation of pharmaceutical compounds and other organic chemicals. Additionally these compounds may be useful as water soluble oxidants and as water soluble antimicrobial agents. These and other advantages will be apparent from the detailed description below.
The compounds of this invention are water-soluble or water-dispersible compounds represented by the following Structure I:
R1xe2x80x94SO2xe2x80x94C(R2)R3xe2x80x94(CO)mxe2x80x94(L)nxe2x80x94SGxe2x80x83xe2x80x83I
wherein R1 is a substituted or unsubstituted aliphatic or cyclic group of any size as long as the antifoggant remains soluble or readily dispersible in water. Substituted or unsubstituted aliphatic groups for R1 include monovalent groups having 1 to 20 carbon, nitrogen, sulfur, and oxygen atoms in the chain including, but not limited to, chains that include one or more substituted or unsubstituted alkyl groups having 1 to 10 carbon atoms, substituted or unsubstituted alkenylene groups having 2 to 20 carbon atoms, substituted or unsubstituted alkylenearylene groups having 7 to 20 carbon atoms in the chain, and combinations of any of these groups, as well as combinations of these groups that are connected with one or more amino, amido, carbonyl, sulfonyl, carbonamido, sulfonamido, thio, oxy, oxycarbonyl, oxysulfonyl, and other connecting groups that would be readily apparent to one skilled in the art. The various types of useful aliphatic groups would be readily apparent to one skilled in the art. Preferred aliphatic groups for R1 include substituted or unsubstituted t-butyl groups and trifluoromethyl groups.
R1 can also be substituted or unsubstituted cyclic groups including substituted or unsubstituted carbocyclic aryl groups having 6 to 14 carbon atoms to fonn the cyclic ring, substituted or unsubstituted cycloalkylene groups (having 5 to 10 carbon atoms to form the cyclic ring) and heterocyclic groups (having 5 to 10 carbon, nitrogen, sulfur, or oxygen atoms to form the cyclic ring), both aromatic and non-aromatic. The various types of cyclic groups would be readily apparent to one skilled in the art.
Preferred cyclic groups for R1 include substituted or unsubstituted aryl groups having 6 to 10 carbon atoms to form the cyclic ring. Substituted or unsubstituted phenyl groups are most preferred. Methyl groups are preferred substituents on the phenyl group.
In Structure I, R2 and R3 are independently hydrogen or bromine as long as one of them is bromine. Preferably, both R2 and R3 are bromine.
In addition, L is a substituted or unsubstituted divalent linking group, and more preferably an aliphatic linking group that can have the same definition as R1 except that L is divalent. Thus, one skilled in the art would be able to determine suitable L groups that would serve the desired purpose while maintaining compound water solubility or dispersibility. Preferably, L is xe2x80x94NH-alkylene wherein xe2x80x9calkylenexe2x80x9d is substituted or unsubstituted and has 1 to 10 carbon atoms (more preferably 1 to 3 carbon atoms).
Substituents on R1 and L can be any chemical moiety that would not adversely affect the desired function of the antifoggant and can include, but are not limited to, alkyl, aryl, heterocyclic, cycloalkyl, amino, carboxy, hydroxy, phospho, sulfonamido, sulfo, halo and other groups that would be readily apparent to one skilled in the art. The number of substituents is limited only by the number of available valences (available hydrogen atoms). Alkyl groups are preferred substituents for cyclic R1 groups. However, as would be apparent, the antifoggants can have multiple sulfo, carboxy, phospho, and sulfonamido groups that impart water solubility to the molecule. Further, in Structure I, m and n are independently 0 or 1, and preferably, both are 1.
SG can be any suitable solubilizing group which has a pKa of 8 or less and which does not interfere with the antifogging activity of the compound. SG may be in the free acid form or it may be a salt, particularly a suitable metal (for example, alkali metal salt) or ammonium ion salt. Preferably, SG is a salt. When SG is in its free acid form, the salt can be generated in situ by neutralization with any basic material commonly used by one skilled in the art. Preferably SG is a carboxy, phospho, sulfo or sulfonamido group. When SG is a sulfonamido group, it may be xe2x80x94SO2Nxe2x88x92COR4M+, or xe2x80x94NSO2R4M+ with R4 being a substituted or unsubstituted aliphatic or cyclic group that is defined the same as for R1, although R1 and R4 can be the same or different in a particular compound. Preferably, SG is a carboxy or sulfo group (or salts thereof), particularly when both m and n are 1. However, when m and n are both 0, SG is not a sulfo (or salt thereof) or a sulfonamido (or salt thereof) and when m is 0 and n is 1, either L is not an alkylene group or SG is not a carboxy (or salt thereof). In one embodiment when m and n are both 0, SG is a carboxy (or salt thereof) or phospho (or salt thereof). In another embodiment when m is 0, n is 1 and L is an alkylene group, SG is sulfo (or salt thereof), phospho (or salt thereof), or sulfonarnido (or salt thereof).
M+ is a suitable cation such as a metal cation (preferably alkali metal ion) or an ammonium ion. When M+ is a hydrogen atom the resulting free acid can be easily solubilized by neutralization with any convenient base, such as, for example, potassium hydroxide or sodium bicarbonate.
Representative antifoggants useful within the practice of this invention include the following compounds: 
The compounds represented by Structure I can be prepared using starting materials and procedures that would be readily apparent to one skilled in the art. For example, compounds wherein m is 1 (and n is 0 or 1) can be prepared by reacting a salt of a sulfinic acid (such as p-toluenesulfinic acid, sodium salt) with a 2-bromomethylcarbonyl derivative, followed by bromination of the resulting sulfone using molecular bromine or another suitable brominating agent.
Instead of using the salt of a sulfinic acid, an aromatic or aliphatic thiol can be condensed with the 2-bromomethylcarbonyl derivative followed by oxidation of the thioether to a sulfone and then subsequent bromination.
Some 2-bromomethylcarbonyl derivatives can be prepared by reacting bromoacetylbromide with amines such as taurine, as described in U.S. Pat. No. 5,091,298 (Parton et al), with glycine, as described in the Journal of the Korean Society of Textile Engineers and Chemists, p 13, December 1981 (Hwang et al), or with methanesulfonamide, as described in U.S. Pat. No. 5,620,989 (Harrison et al).
Monobromination can be achieved by using only one equivalent of a source of bromine, using a less active brominating agent, or by adjusting reaction conditions as one skilled in the art would readily understand. A useful reagent capable of being a water-soluble brominating agent is the inventive compound represented by structure 1. For example, when one mole of inventive antifoggant A-1 is added to an alkaline solution of the unbrominated precursor of A-1, two moles of inventive antifoggant A-20 are formed almost instantaneously at room temperature. This reaction also occurs at lower pH, but more slowly. The use of the water-soluble inventive antifoggant A-1 as a brominating agent produces one mole of the water soluble inventive antifoggant A-20 as a reaction product. This is particularly helpful when the isolation and purification of a water-insoluble bromination product is desired. This will be exemplified later for the preparation of inventive antifoggant A-24.
By xe2x80x9cwater-solublexe2x80x9d or xe2x80x9cwater-dispersiblexe2x80x9d in defining the antifoggants is meant that the compounds are readily dissolved or dispersed in water. Therefore, their use in silver halide emulsions and photographic elements alleviates the need for volatile organic solvents and circumvents the disadvantages of using solid particle dispersions. In order to be xe2x80x9cwater-solublexe2x80x9d or xe2x80x9cwater-dispersiblexe2x80x9d, it should be possible to add between 0.1 g and 500 g of the antifoggant to 1000 mL of water. Optimally, it should be possible to add between 50 g and 200 g of the antifoggant to 1000 mL of water. The antifoggants can be used individually or in combination in the elements of this invention. Generally, they are present in an amount of at least 0.0001 mol/mol of total silver. Preferably, they are present in an amount of from about 0.001 to about 0.1 mol/mol of total silver.
The antifoggant compounds may be added to any layer where they are in reactive association with the silver halide. By xe2x80x9cin reactive association withxe2x80x9d it is meant that the compounds must be contained in the silver halide emulsion layer or in a layer whereby they can react or interact with, or come in contact with, the silver halide emulsion. Preferably, the antifoggants are included in the one or more emulsion layers, but during manufacture, they can also be incorporated into interlayers, underlayers, and protective topcoat layers on the frontside of the support. If they are placed in a non-emulsion layer, they tend to migrate into the emulsion layer(s) where they become effective in reducing Dmin. The antifoggant compounds may be added to the photographic emulsion using any technique suitable for this purpose.
Photographic emulsions are generally prepared by precipitating silver halide crystals in a colloidal matrix by methods conventional in the art. The colloid is typically a hydrophilic film forming agent such as gelatin, alginic acid, or derivatives thereof.
The crystals formed in the precipitation step are washed and then chemically and spectrally sensitized by adding spectral sensitizing dyes and chemical sensitizers, and by providing a heating step during which the emulsion temperature is raised, typically from 40xc2x0 C. to 70xc2x0 C., and maintained for a period of time. The precipitation and spectral and chemical sensitization methods utilized in preparing the emulsions employed in the invention can be those methods known in the art.
Chemical sensitization of the emulsion typically employs sensitizers such as: sulfur-containing compounds, e.g., allyl isothiocyanate, sodium thiosulfate and allyl thiourea; reducing agents, e.g., polyamines and stannous salts, noble metal compounds, e.g., gold, platinum, and polymeric agents, e.g., polyalkylene oxides. As described, heat treatment is employed to complete chemical sensitization. Spectral sensitization is effected with a combination of dyes, which are designed for the wavelength range of interest within the visible or infrared spectrum. It is known to add such dyes both before and after heat treatment.
After spectral sensitization, the emulsion is coated on a support. Various coating techniques include dip coating, air knife coating, curtain coating and extrusion coating.
The antifoggants may be added to the silver halide emulsion at any time during the preparation of the emulsion, i.e., during precipitation, during or before chemical sensitization or during final melting and co-mixing of the emulsions and additives for coating. More preferably these compounds are added after precipitation and washing and most preferably during or directly after chemical sensitization of the final melt.
The compounds of the invention may be used in black and white elements, single color elements or multicolor elements. Multicolor elements contain image dye-forming units sensitive to each of the three primary regions of the spectrum. Each unit can comprise a single emulsion layer or multiple emulsion layers sensitive to a given region of the spectrum. The layers of the element, including the layers of the image-forming units, can be arranged in various orders as known in the art. In an alternative format, the emulsions sensitive to each of the three primary regions of the spectrum can be disposed as a single segmented layer.
A typical multicolor photographic element comprises a support bearing a cyan dye image-forming unit comprised of at least one red-sensitive silver halide emulsion layer having associated therewith at least one cyan dye-forming coupler, a magenta dye image-forming unit comprising at least one green-sensitive silver halide emulsion layer having associated therewith at least one magenta dye-forming coupler, and a yellow dye image-forming unit comprising at least one blue-sensitive silver halide emulsion layer having associated therewith at least one yellow dye-forming coupler. The element can contain additional layers, such as filter layers, interlayers, overcoat layers, and subbing layers.
If desired, the photographic element can be used in conjunction with an applied magnetic layer as described in Research Disclosure, November 1992, Item 34390 published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire PO10 7DQ, ENGLAND, the contents of which are incorporated herein by reference. Further, the photographic elements may have an annealed polyethylene naphthalate film base such as described in Hatsumei Kyoukai Koukai Gihou No. 94-6023, published Mar. 15, 1994 (Patent Office of Japan and Library of Congress of Japan) and may be utilized in a small format system, such as described in Research Disclosure, June 1994, Item 36230 published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire PO10 7DQ, ENGLAND, and such as the Advanced Photo System, particularly the Kodak ADVANTIX films or cameras.
In the following Table, reference will be made to (1) Research Disclosure, December 1978, Item 17643, (2) Research Disclosure, December 1989, Item 308119, (3) Research Disclosure, September 1994, Item 36544, and (4) Research Disclosure, September 1996, Item 38957, all published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire PO10 7DQ, ENGLAND, the disclosures of which are incorporated herein by reference. The Table and the references cited in the Table are to be read as describing particular components suitable for use in the elements of the invention. The Table and its cited references also describe suitable ways of preparing, exposing, processing and manipulating the elements, and the images contained therein. Photographic elements and methods of processing such elements particularly suitable for use with this invention are described in Research Disclosure, February 1995, Item 37038, published by Kenneth Mason Publications, Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire PO10 7DQ, ENGLAND, the disclosure of which is incorporated herein by reference.
The photographic elements can be incorporated into exposure structures intended for repeated use or exposure structures intended for limited use, variously referred to as single use cameras, lens with film, or photosensitive material package units.
The following examples are intended to illustrate, but not to limit, the invention: